152 



UNITED STATES MINERAL RESOURCES 



those already mentioned in the New England States. 

 Additional bodies of cobalt minerals associated 

 with iron ore of contact metamorphic origin, such as 

 those at Cornwall, Pa., probably lie hidden in south- 

 eastern Pennsylvania. Perhaps as many as two dozen 

 bodies might occur at depth at the sites of magnetic 

 anomalies in the region. The discovery of the hidden 

 body that is now the Grace mine was facilitated by 

 such data. 



The chances for finding more massive sulfide 

 bodies of the Ducktown type seem good all through 

 the Appalachian region, especially in the southern 

 Piedmont and Blue Ridge provinces. 



Possibilities for the discovery of more ores of the 

 Mississippi Valley type are good. The chances of 

 such ore containing some cobalt and nickel seem 

 favorable, because the ore already known in the mid- 

 continental United States forms one of the world's 

 great concentrations of metal sulfides, including 

 cobalt and nickel, and two such cobalt-bearing dis- 

 tricts, widely spaced, are known. Large deposits may 

 still be found in extensions of known districts. The 

 lead deposits of northern Arkansas might contain 

 cobalt, especially indicated by the local bodies rich 

 in pyrite. The known ore deposits may be the ex- 

 posed parts of zoned districts in which the cobalt- 

 rich parts are still hidden beneath barren caprocks. 



Large new deposits of laterite probably will not be 

 found in the United States. In many tropical areas of 

 the world, however, substantially large hypothetical 

 (and speculative) resources will likely be found, 

 especially in some of the more remote regions. 



More areas of sea bottom containing manganese 

 nodules will be found and evaluated. When practical 

 techniques for mining and extracting the metals 

 from the nodules have been developed, large re- 

 sources of cobalt will become available. 



SPECULATIVE RESOURCES 



The foregoing discussions suggest that the specu- 

 lative resources of cobalt in the United States and 

 the rest of the world are large. 



Additional mafic and ultramafic rocks in the Ap- 

 palachian and Cordilleran regions might be found 

 containing valuable resources of cobalt. More mas- 

 sive sulfide bodies might be found at greater depth 

 in Precambrian rocks of the Great Lakes region. 

 Cobalt in commercial quantities might occur in large 

 transverse veins in the copper region of the Upper 

 Michigan Peninsula. In 1902 a shipment of arsenide 

 minerals from the Mohawk mine went to the Cam- 

 den Nickel Works and was "treated successfully" 

 for cobalt, but records show no further production 

 from that area. 



Deposits of the Cornwall type may well occur 

 along the edges of the diabase intrusions in the Tri- 

 assic trough in Virginia, Maryland, and New Jersey. 

 The Triassic region of New Jersey may well have 

 more sills and lopolithic bodies at depth that are in 

 contact with Paleozoic carbonate rocks that were 

 most favorable for the formation of large ore de- 

 posits. Replacement deposits might occur along the 

 diabase contact of the Triassic trough of the Con- 

 necticut Valley. 



Additional districts containing cobalt-bearing sul- 

 fide ores of the Mississippi Valley type probably oc- 

 cur elsewhere in the United States and in the world. 

 Geologic indications of such a district are exposed in 

 the cobalt-bearing veins near Rossie, N.Y., and in 

 nearby southern Ontario. These deposits do not seem 

 to be related to the large zinc deposits of the Balmat- 

 Edwards district. New York. 



Metamorphic-hydrothermal deposits similar to 

 those in the Thompson-Moak Lake district, Mani- 

 toba, probably occur elsewhere in the world. The 

 possibilities are excellent in the great Precambrian 

 Shield areas of Canada, Africa, Australia, and Eura- 

 sia for locating major ore districts of the Sudbury 

 type, as has been shown by the many major dis- 

 coveries since World War II. 



PROSPECTING TECHNIQUES 



Inasmuch as cobalt is produced chiefly as a by- 

 product of mining other ores, relatively little direct 

 exploration for cobalt deposits has been needed or 

 undertaken, except during domestic national emer- 

 gencies when foreign supplies were restricted or un- 

 available. These exploration efforts generally have 

 been directed toward careful examination of areas 

 of known cobalt deposits and occurrences using con- 

 ventional geologic, geophysical, and geochemical 

 techniques. Pyrrhotite deposits are particularly easy 

 to identify by known geophysical techniques, and 

 cobalt is easy to identify with geochemical prospect- 

 ing methods. Techniques for determining trace 

 amounts of cobalt are well known (Almond, 1953; 

 Hawkes, 1957 ; Ward and others, 1963 ; Canney and 

 Nowlan, 1964; Warren and others, 1964). Cobalt is 

 more mobile than copper and may be useful as a 

 pathfinder for deposits of associated elements (Can- 

 ney and Wing, 1966). Biogeochemical prospecting 

 for cobalt holds promise (Warren and Delavault, 

 1957 ; Tooms and Jay, 1964) . 



Applications of geochemical prospecting tech- 

 niques have successfully found the extension of a 

 vein in the Quartzburg district, Oregon, and out- 

 lined the Blacktail ore body as well as a large halo of 

 cobalt in the Blackbird district, Idaho (Canney and 



